jan 1, 1974 - Hawking Radiation (1974) Einstein's theory conflicted with quantum physics. The boundary of a black hole couldn't exist in the smooth spacetime, if the black hole is composed of granular energy required by quantum physics. Hawking solved this with Hawking Radiation: black holes are emitting energy. Quantum Gravity is still a working concept.
Added to timeline:
Date:
jan 1, 1974
Now
~ 51 years ago